1. Field of the Invention
The present invention relates to an illumination apparatus and projection apparatus and, more particularly, to an illumination apparatus and projection apparatus which are suited for a liquid crystal projector for enlarging/projecting an image formed by a liquid crystal display device (liquid crystal panel) on a screen or wall through a projection lens.
2. Related Background Art
Various liquid crystal projectors have been proposed, which are designed to illuminate a liquid crystal panel with a light beam from a light source and enlarge/project an image based on transmitted or reflected light from the liquid crystal panel on a screen or wall through a projection lens.
FIG. 5 is a schematic view showing the main part of a conventional liquid crystal projector. The illumination optical system of the liquid crystal projector in FIG. 5 uses a combination of a light-emitting tube 1, parabolic mirror 19, and a pair of lens arrays 15 and 16.
Referring to FIG. 5, the white light emitted from a light-emitting portion 1c of the light-emitting tube (light source) 1 is almost collimated by the parabolic mirror 19, and the first lens array 15 forms the light source image from the light-emitting tube 1 on the center of each lens portion of the second lens array 16.
The focal length of the first lens array 15 is almost equal to that of the second lens array 16. The distance between the first and second lens arrays 15 and 16 is almost equal to the focal length-of the first lens array 15. The light beam focused by the first lens array 15 is separated into P-polarized light and S-polarized light by a polarization separating layer 5B of a polarization converting element 5. The P-polarized light is transmitted through the polarization separating layer 5B, and the S-polarized light is reflected by the layer 5B. The P-polarized light is phase-converted by a xcex/2 retardation plate 5A to be aligned with the polarization axis of the S-polarized light.
All the light beams emitted from the polarization converting element 5 become polarized light beams having polarization axes in the same direction. The polarization converting element 5 has a blind-like light-shielding plate 5C.
The light beam emitted from the polarization converting element 5 is deflected by a first condenser lens 6 to be superimposed on display portions 8R, 8G, and 8B of image modulating units which are made up of liquid crystal panels for separately modulating R, G, and B light beams. The red light of the light beam emerging from the first condenser lens 6 is reflected by a dichroic mirror DM1, and the remaining green light and blue light are transmitted therethrough.
The red light reflected by the dichroic mirror DM1 is guided to the display portion 8R of the red image modulating unit through a reflecting mirror M1 and second condenser lens 7R. The light transmitted through the dichroic mirror DM1 is separated into green light and blue light by a dichroic mirror DM2. The green light is reflected by the dichroic mirror DM2 to be guided into the display portion 8G of the green image modulating unit through a second condenser lens 7G.
The blue light transmitted through the dichroic mirror DM2 is focused by a condenser lens 11 and reflected by a reflecting mirror M2. The reflected light is guided to the display portion 8B of the blue image modulating unit by a relay lens 12 through a reflecting mirror M3 and second condenser lens 7B.
Referring to FIG. 5, polarizing plates P1 and P2 are set on the incident and exit sides, respectively. The second condenser lenses 7R, 7G, and 7B serve to focus the light beam emerging from the first condenser lens 6 onto the entrance pupil of a projection lens 10. A cross-dichroic prism 9 is placed between the projection lens 10 and the display portions 8R, 8G, and 8B of the image modulating units to perform color synthesis.
The projection lens 10 is designed to be telecentric with respect to the display portions 8R, 8G, and 8B of the image modulating units. The incident tangle on the dichroic film surface of the cross-dichroic prism 9 remains constant throughout the entire dichroic film, thereby preventing color irregularity due to changes in incident angle on the dichromic film.
The light beams respectively modulated by the display portions 8R, 8G, and 8B of the image modulating units are subjected to color synthesis in the cross-dichroic prism 9. The resultant image is enlarged/projected on a screen (not shown) through the projection lens 10.
To reduce the sizes of the pair of lens arrays 15 and 16 in the optical axis direction in the general liquid crystal projector shown in FIG. 5, the microlenses constituting the pair of lens arrays 15 and 16 may be reduced in size.
However, the size of the blind-like polarization converting element 5 used in combination with the pair of lens arrays 15 and 16 must be reduced in proportion to the sizes of the lens arrays 15 and 16. This makes it difficult to manufacture the micro-prism of the polarization converting element 5. In addition, the loss of light is increased by a film omission on a peripheral portion of the surface 5B forming the polarization separating layer of the prism (vignetting on the deposition surface due to a mask for preventing a deposition material from spreading to a surface other than the deposition surface in a deposition process). For this reason, the size of each lens of each lens array cannot be reduced beyond a certain limit. This makes it difficult to reduce the sizes of the pair of lens arrays in the optical axis direction.
It is an object of the present invention to provide an illumination apparatus which can reduce the size of an illumination optical system in the optical axis direction by using three lens arrays having appropriate refracting powers in part of the illumination optical system without decreasing the size of each lens of the lens arrays, and a projection apparatus using the illumination apparatus.
According to the present invention, there is provided an illumination apparatus for illuminating a display device with a light beam from a light source through an illumination optical system, the illumination optical system including a first lens array unit having a plurality of positive lens portions juxtaposed with each other, a second lens array unit having a plurality of negative lens portions juxtaposed with each other, and a third lens array unit having a plurality of positive lens portions juxtaposed with each other, the first to third lens array units being sequentially arranged from a light source side.
This apparatus further comprise a reflector for reflecting some light component of a light beam from the light source and guiding the light component as a collimated light beam to the first lens array unit.
In this apparatus, an image-side focal point of combined system of the first and second lens array units is located-near the third lens array unit, and an object-side focal point of a combined system of the second and third lens array units is located near the first lens array unit.
In this apparatus, the reflector is made of an elliptic mirror or parabolic mirror.
This apparatus further comprises a lens having a negative refracting power between the light source and the first lens array unit.
In this apparatus, each of the plurality of positive lens portions of the first lens array unit is made of a plano-convex lens having a convex surface facing the light source side, each of the plurality of negative lens portions of the second lens array unit is made of a plano-concave lens having a flat surface facing the light source side, and each of the plurality of positive lens portions of the third lens array unit is made of a plano-convex lens having a flat surface facing the light source side.
The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description in conjunction with the accompanying drawings and the appended claims.